Today's business practices often require that tools be traced in production and maintenance environments. Generally, an identification data (ID) device attached to each tool is required. For productivity purposes, such an ID device needs to be read remotely and automatically by electronic readers. Automation reduces errors in information capture and allows for more accurate and more regular inventory management. This requires ID devices, which can communicate.
Radio frequency identification (RFID) is a preferred solution as radio frequency communication allows a diffuse transmission and is tolerant to radio frequency ID devices being hidden, as opposed to optical solutions, which are more directional and quite intolerant to blocking bodies lying in the transmission path. The use of RFID transponders (commonly referred to as RFID tags) is an efficient and economical method for systems for tracking and tracing items within an organization. Producers can check the location of items, in real time, by remotely accessing the data being transmitted by RFID tags attached to those items. Therefore, RFID tags are widely used for the identification and the tracking of items, particularly for items in a shop or a warehouse environment.
Such RFID systems can also be used for tracking and tracing tools in tool cabinets and can provide the following functions: detect the input or output of tools in or from the tool cabinet, inventory of tools stored in each particular tool cabinet and globally in all the tool cabinets, avoid foreign object damage, establish links between the tools and the personnel using them and allow tools monitoring (maintenance, check, periodic control). A RFID system should in particular allow verifying the content of the tool cabinets used within the organization.
Tool cabinets and tools are typically used for example when maintenance personnel go on missions to troubleshoot systems. Tool tracking and tracing is beneficial not only for inventory purpose of the tools, but also for ensuring that tools required for a particular maintenance intervention are effectively in the tool cabinet and have not been left in the field, for example preventing left behind tool from causing foreign object damage, (for example a tool left in a turbine).
In principle, either LF/HF RFID or UHF RFID technologies could be used. However, UHF RFID technology is a preferred solution because of the following issues inherent to LF/HF RFID technology. LF/HF inductive loop antennas are heavier and more expensive than UHF antennas, and do not work properly on or near conductive surfaces (both for the RFID tag and the UHF RFID reader). LF/HF RFID technology requires additional magnetic spacer or coating (such as ferrite) to canalize or channelize the magnetic field, which implies a complex and expensive implementation. Additionally, the LF/HF alternative magnetic field induces eddy currents in the walls of the tool cabinet, generating energy losses and heat in the toolbox, resulting in additional cost for the system to evacuate this energy.
A standard UHF RFID system comprises a reader connected to at least one antenna, and detects RFID transponders or tags within the volume covered by the radiative electromagnetic field generated by the system antennas. Typically, the external walls and doors of tool cabinets are made of metal. The radiofrequency signals, which must be exchanged between the UHF RFID system and a RFID tag, cannot effectively penetrate the external conductive walls and doors of such tool cabinets. The RFID tags which mark the tools stored in the tool cabinet cannot be detected in a metal cabinet if the RFID system is placed outside such closed tool cabinets.